const-correct cast in hashing
const-correct cast in hashing

The C++ build notices that a const pointer is cast to another const
pointer by way of a non-const type.  This makes the intermediate type
in the cast const as well.

draegtun/ren-c,rgchris/ren-c,giuliolunati/ren-c,hostilefork/rebol,giuliolunati/ren-c,rgchris/ren-c,codebybrett/ren-c,codebybrett/ren-c,codebybrett/ren-c,draegtun/ren-c,kealist/ren-c,kealist/ren-c,codebybrett/ren-c,rgchris/ren-c,codebybrett/ren-c,giuliolunati/ren-c,hostilefork/rebol,giuliolunati/ren-c,rgchris/ren-c,hostilefork/rebol,kealist/ren-c,draegtun/ren-c,kealist/ren-c,kealist/ren-c,draegtun/ren-c,draegtun/ren-c,hostilefork/rebol,rgchris/ren-c,draegtun/ren-c,kealist/ren-c,codebybrett/ren-c,hostilefork/rebol,giuliolunati/ren-c,hostilefork/rebol